fixup! Bug 9173: Change the default Firefox profile directory to be relative.

Force `GenerateAppUserModelID` to use the profile directory in portable
mode.

widget/windows/WinTaskbar.cpp

@@ -209,6 +209,19 @@ bool WinTaskbar::GenerateAppUserModelID(nsAString& aAppUserModelId,
   // If marked as such in prefs, use a hash of the profile path for the id
   // instead of the install path hash setup by the installer.
   bool useProfile = Preferences::GetBool("taskbar.grouping.useprofile", false);
+
+  {
+    // For portable mode, force the AUMID to be based on the profile directory
+    // instead of reading it from the registry.
+    bool isPortable = true;
+    // Do not even check if taskbar.grouping.useprofile is already true.
+    if (!useProfile &&
+        NS_SUCCEEDED(gDirServiceProvider->GetIsPortableMode(&isPortable)) &&
+        isPortable) {
+      useProfile = true;
+    }
+  }
+
   if (useProfile) {
     nsCOMPtr<nsIFile> profileDir;
     NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,